So we're talking about where to mount the two magnetometers in Bob Lund's RV-8. Jason Smith at Aerotronics suggested that a tail mount of a Garmin magnetometer is not passing the interference check during calibration (we're talking RV-8--tail location is fine in my RV-6). Steve at GarminX was also very encouraging. So we decided to try a wingtip mount in spite of the heavy iron pipe that is in the leading edge of the ailerons. That was a concern. Here are some pictures:

And the GRT Mini magnetometer installation in the opposite wint tip:

We did the Garmin Magnetometer Interference Test today for the first time and it passed! The highest interference level we got was 64% of the limit during full left aileron deflection, but apparently it was still well within the limits. We will report later on the GRT magnetometer results when we get to it.

We rolled the airplane out of the hangar today for the first time, ready for first engine start in the morning. More later.

Mark, I would say it would be fine but I'll defer to the experts. I have mounted magnetometers together in the past with no issues. Given the choice, however, I would want to eliminate any possibility for interference.

Almost none (2% was what I recall). If I had to do it over, I would have moved the magnetometers forward more because of this, especially since our strobes are LEDs. But I was concerned about the strobes, nav and landing lights in the wing tips.

I have the GMU22 in my RV-8As wingtip, but mounted a little farther forward. My biggest source of interference is the landing light, but it's still well within limits. Both the landing lights and position/strobes are LED.

I had my Dynon D10A magnetometer mounted in the right wingtip and it seemed to work fine. Of course, I didn't have much to compare it to.

When I changed to GRT MiniX's I put the magnetometer on the same mount in the right wing. During calebration it seemed to work fine and showed that it was a good place. However, it actual use I had large (10-15 degree) variations with my HXr. (HXr magnetometer mounted in fuse about 12" behind baggage real wall). My variations occurred only on 45 degree's off cardinal headings, and was worse to the SW. I moved the magnetometer forward in the right wingtip to get away from the aileron rod and that didn't change anything.

I finally just mounted it next to the one in the rear fuse and now they are both exactly the same on all headings. I've swung it a couple times and they match compass roses and runway mag headings exactly.

I'm just throwing this out. In my 8 I could not get the wing mount to give accurate headings.

We just did this one with the Garmin unit a couple of months ago. The wing tip works well if you mount the unit halfway between the spar and the back of the main wing body. The only thing we found was for the strobes and other lights in that wing tip we needed to run a ground wire into the main center section of the cabin, for all the lights and strobe. If you don't use the wing as your ground conductor from the outboard end of the wing, there will not be an electrostatic field in parted to the wing structure close to the magnetometer. The only thing that you have then, close to the unit is the steel in the hinge bolts, counter balance weight, and wing tip screws ( use stainless ). We got 30-40% or there about.
Hope this helps. Yours as always. R.E.A. III #80888

How about the nut plates for the wing tip attach screws? I don't seem to be able to find any #6 size made of stainless. Is using steel Ok in this situation, or will it affect the magnetometer?
Regards,
Tom.

How about the nut plates for the wing tip attach screws? I don't seem to be able to find any #6 size made of stainless. Is using steel Ok in this situation, or will it affect the magnetometer?
Regards,
Tom.

We did find some in S.S., but left them standard for the first test and found the ones close to the unit did not amount to enough galvanic field to amount to changing them out. We just used the S.S. screws, ran the new ground wire and kept on going. Hope this helps. Yours, R.E.A. III #80888

The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.